Rivers tend to generate in coast lines and very deeply in oceans 

Via data packs (Rivers.zip) I tinted river red and beach green so it's visible and you can see beaches are placed correctly because they have to surround biomes, but rivers generate there.
Swamps were changed so they don't generate that deep in oceans, so it would be great if they changed this too

With the following seeds you can use the F3 screen to sea the river biomes:

(Seed: -4753858570600020860; Pos: -7187 84 1506)

(Seed: -753111143593067491; Pos: -3721 107 787)

(Seed: 93366035475932059; Pos: -7187 84 1506; Also a bifurcated small warm ocean at -5775 92 -4749 (not shown))